I should've never have touched this thing.....

[PhilthMonger]

for the past 3 months I've been re-constructing everything on the GN....had a blown turbo, cracked headers, and oil leaks from every orifice imaginable. So, I basically pulled the motor and resealed everything. while I was there I threw in a converter from Pat's Performance, a nice PTE turbo, blah blah blah everything is basically new. the moment of truth comes, to fire the beast back to life....no start. major backfiring in the intake....I really hope I didn't blow the intake manny gasket doing this by the way. anyway, I re-installed my cam sensor. brought it up to tdc to what I thought was the compression stroke, which in my demented mind means valves closed/ piston coming up and blowing air out the plug hole....please correct me if I'm wrong. I went 25 deg after tdc and stuck the sensor in with the harness facing the driver's side. (gear dowel to the back) I got kirban's cam sensor tool, and set it according to the led. same backfiring, wont start. for kicks, I did it again on only on the opposite exhaust stroke, same thing. the throttle body elbow gets real hot due to all this backfiring. I'm definintely getting spark and fuel.....just in the wrong direction. I'm kinda leaning toward crank sensor on this one, it was caked in oily sludge and dirt when I removed it....I just cleaned and reinstalled. Would a bad crank sensor cause such violent backfiring in the intake? Am I way off on this? I have alot of experience in turbo imports, this is the first GN I have ever touched. I have to say, the archives on this board were very helpful to this point. another thing worth mentioning, I had a new PTE chip burned for my new injectors. I have tried starting the car with this chip as well as the old stock chip and everything is acting the same. This car did in fact run before I tore it up! any ideas or suggestions would be greatly appreciated!

 

[SPECTRA PREMIUM]

Let's start at the basic.
The Cam is in right! Right?
The Cam can be off 180 and engine would start anyways.
Check your Crank Sensor, or replace it.
Make sure that the clearances are good at the Trigger..

Off topic...did you change Valve Covers and installed Roller Rockers? I had an engine once it didn't want to start because the Customer purchased a set of BGC Covers and the Stock Rockers were grinding off the Valve Covers leaving the Valves open.

Joe

 

[PhilthMonger]

the motor was apparently rebuilt at some point, I got it off a kid who let it go to hell....I did not remove the cam, however I did check the timing when I had the front case off, everything looked great. pretty much stock valvetrain, nothing special. the car actually ran pretty decent considering it's problems. its when I try to clean things up a bit is when I have problems. the crank sensor is easy enough to change....I was tempted to change it before I put it back just for the fact that it was so dirty from all the oil crud caked on it....

 

[SPECTRA PREMIUM]

Just clear what I wrote.
I meant that the Cam was in right, but if you said that ran. So delete that idea.
The Cam Sensor will work even if it's 180 off..
It's a stupid problem, go slow.

 

[John Larkin]

Crank sensor is ignition timing, cam sensor is fuel timing. If you have both, then the sensors are likely good. Synchronizing them is now the key obviously. Firing order could have much to do with it, as well as the likeliness of the cam sensor being 180 degrees off. Pull it out, rotate the engine 180 degrees and drop it back in. You also need to ensure with a cam sensor tool or a voltmeter that the cam sensor is set in the window; it can do bad things if it is out of the window. There is a setting procedure on www.gnttype.org Good luck!

 

[sumnerw]

I remember very clearly the "moment of truth" for the first engine I ever rebuilt. Cranked, caught, backfired horribly. Shut it down. Looked and looked and looked....

Had two plug wires reversed. DOH!

Fixed.

Cranked, caught, ran great!

Good luck,
Buzz White in Houston, TX (sumnerw@flash.net)

 

[PhilthMonger]

hope I haven't been misinformed about firing order...this is what I got...

Firewall

6 5
4 3
2 1

Radiator


now on the coilpack..... top row 6,4,2

bottom row 1,3,5

....that is from memory as I'm not home right now, coil pack not necessarily in that order. the coil pack is numbered though, so I'm pretty sure I got it ok on the coilpack....

 

[VIN7]

now on the coilpack..... top row 6,4,2

Should be

now on the coilpack..... fire wall 1,5,3

bottom row 4,2,6

Mike

 

[bar87]

i think u got it backwards

cyl 1,3 & 5 are nearest the firewall
2,4 & 6 are nearest the doghouse (intake)
is that how u have it?

 

[PhilthMonger]

hmmm....no, I have the odds in front of the evens.....I just put it back the way I took it off, the bracket only bolts on one way, two bolts up front and one out back. can the coil pack be removed from that bracket? I sure as hell didn't do it, but the car was a basket case to begin with. on ANOTHER note.....sitting here at work contemplating what I've done, I was picturing the crank sensor.....there are two slots. I think I may have installed it on the wrong slot I guess we'll find out in a couple hours when I get home. I'll really kick myself in the ass if that's the problem

 

[VIN7]

Doesn't really matter if the evens/odds are reversed, it is a wastespark system after all. The coil pack can be flipped around on the module to get the orientation correct.


Coil Pack Order Thanks Caspers


Mike

 

[PhilthMonger]

that may explain why my magnecors dont fit well either.....

 

[PhilthMonger]

in case anyone is interested....I was hit with a 3 punch combo on this pig....crank sensor was a little crusty, replaced. fuel pressure did not hold properly, threw in a nice walbro 340, and last but not least, a weak coilpack. the funniest thing about this, the car actually ran before i took it apart. go figure! I guess I should've left everything dirty rather than try to clean it

 

[GNSS]

Did you have the intake off?
If you did you might want to double check the injector harness and make sure you connected the right ones to the right injectors.
They should be marked.

Jeff

 

[PhilthMonger]

the last response was just to let everyone know that the car runs now, figured if someone else had a problem and came across this, they would know what actually fixed my particular problem. thanks anyway though!